1. Field of the Invention
This invention relates to a power circuit for a photographic camera, and more particularly to a power circuit for supplying electric current to an electromagnetically driven shutter or diaphragm in a photographic camera.
2. Description of the Prior Art
It has been desired to reduce the number of parts of a camera to reduce the weight and size thereof. By simplifying the structure of the camera, it is also possible to simplify the operation and lower the manufacturing cost thereof. From the viewpoint of simplification, it is undesirable to drive the various mechanisms in the camera only by mechanical driving means. Therefore, as a means for controlling the shutter mechanism and the diaphragm mechanism there has been proposed and put into practice an electric control means employing an exposure control circuit.
Even in these electrically controlled cameras, however, the control mechanisms are driven by a mechanical force as of a spring. For instance, a spring force is charged by an operation to set a shutter mechanism and locked by a lock member, and then, the lock member is released by means of a solenoid or the like which is controlled by an electric circuit. The shutter mechanism is then driven by the force of the charged spring. These cameras employing a spring force to drive the shutter mechanism or the like require a complicated mechanical driving means. Therefore, the structure and operation of these cameras are still complicated and accordingly the manufacturing cost is still high.
In view of the defects inherent in these cameras, it has been proposed to drive the shutter mechanism or diaphragm mechanism by an electromagnetic force by use of a combination of a permanent magnet and a coil. However, since the driving force of the coil depends upon the number of turns of the windings and the amount of electric current flowing therethrough, the number of turns must be increased to obtain a large driving force with cells which, being small enough to load in the limited space within the camera body, are necessarily of low power. An increase in the number of turns of the coil windings results in an increase in the size of the coil, which is undesirable from the viewpoint of manufacture.